Linear slide roller bearing unit

ABSTRACT

A linear slide roller bearing unit for use in, for example, a machining center has a track shaft extending in the longitudinal direction of the linear slide roller bearing unit and having loaded roller rolling surfaces respectively formed on both side surface portions of each of the right and left ridges thereof projecting in the direction of an imaginary oblique line intersecting the horizontal axis at an angle of about 45°. The linear slide roller bearing unit further has a movable table constituted by a long block member disposed so as to straddle the track shaft, the movable table having longitudinal recesses respectively formed in the opposing inner surfaces of skirt portions thereof. A pair of right and left bearing bodies are each constituted by a long block member which is screwed to the corresponding recess in the movable table, each bearing body having a guide ridge projecting from the center of each inner side surface portion of the block member, each guide ridge having one side surface thereof defined as a loaded roller rolling surface confronting the corresponding loaded roller rolling surface of the track shaft and the other side surface defined as a non-loaded roller rolling surface.

BACKGROUND OF THE INVENTION

The present invention relates to a linear slide roller bearing unit suitable for use in various sliding parts such as the table saddle of a machine tool, the slider of a machining center and the slider of a transportation robot for reciprocative transportation of a heavy object.

Generally, a conventional linear slide roller bearing unit of this type has been constructed such that a bearing body of channel-like cross-section is slidably mounted on a track shaft of substantially trapezoidal cross-section through one row of cylindrical rollers. The thus constructed roller bearing unit may, however, disadvantageously cause the skew (oscillation of the longitudinal axes) of the rollers and is unable to provide a large load bearing capacity due to employment of the cylindrical rollers. In addition, since a roller rolling groove for guiding the recirculation of the cylindrical rollers is directly formed in each skirt portion of the bearing body, it is inconveniently difficult to effect turning and grinding operations when forming the roller rolling groove. Further, the construction of the conventional linear slide roller bearing unit unfavorably makes it impossible to adjust the preload applied to the cylindrical rollers interposed between the roller rolling groove on the bearing body and the corresponding roller rolling groove on the track shaft.

SUMMARY OF THE INVENTION

Under these circumstances, the invention aims as its primary object at overcoming the above-described problems of the prior art.

Accordingly, it is an object of the invention to provide a linear slide roller bearing unit capable of preventing any skew of the rollers to ensure smooth running thereof and of increasing its load bearing capacity.

It is another object of the invention to provide a linear slide roller bearing unit which facilitates the machining of the roller rolling groove and makes it possible to freely adjust the preload applied to the rollers within the loaded region.

To these ends, according to the invention, there is provided a linear slide roller bearing unit comprising: a track shaft extending in the longitudinal direction of the linear slide roller bearing unit and having loaded roller rolling surfaces respectively formed on both side surface portions of each of the right and left ridges thereof projecting in the direction of an imaginary oblique line intersecting the horizontal axis at an angle of about 45°; a movable table constituted by a long block member disposed so as to straddle the track shaft, the movable table having longitudinal recesses respectively formed in the opposing inner surfaces of skirt portions thereof; a pair of right and left bearing bodies each constituted by a long block member which is screwed to the corresponding recess in the movable table, each bearing body having a guide ridge projecting from the center of each inner side surface portion of the block member, each guide ridge having one side surface thereof defined as a loaded roller rolling surface confronting the corresponding loaded roller rolling surface of the track shaft and the other side surface defined as a non-loaded roller rolling surface; barrel-shaped rollers adapted to be recirculated along the loaded roller rolling surfaces and non-loaded roller rolling surfaces of the bearing bodies and to come in contact with the loaded roller rolling surfaces on the track shaft when rolling along the loaded roller rolling surfaces on the bearing bodies; and a roller retainer attached to each of the guide ridges so as to face the corresponding inner side surface portion of the associated bearing body and adapted to guide the rollers so that they can recirculate through the space defined between the roller retainer and inner side surface portion, wherein the rollers in the state of serving as loaded rollers are brought into contact with the loaded roller rolling surfaces on the track shaft at a contact angle of about 45° with respect to an imaginary oblique line passing through the center of each of the right and left ridges of the track shaft so that the loaded rollers contacting the loaded roller rolling surfaces on both side surface portions of each ridge are orthogonal to each other.

These and other objects, features and advantages of the invention will become clear from the following description of the preferred embodiments thereof taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings in combination show embodiments of the linear slide roller bearing unit in accordance with the invention, in which:

FIG. 1 is a front elevational view of a first embodiment of the linear slide roller bearing unit in accordance with the invention;

FIG. 2 is a sectional bottom view taken along the line II--II of FIG. 1;

FIG. 3(a) is a vertical sectional view of a bearing body retaining rolling rollers through roller retainers, taken through an intermediate portion thereof in the longitudinal direction;

FIG. 3(b) is a front elevational view of an end portion of the bearing body;

FIG. 3(c) is a plan view of the bearing body;

FIG. 3(d) is a side elevational view of the bearing body;

FIG. 4(a) is a vertical sectional view of a bearing body, taken through an intermediate portion thereof in the longitudinal direction;

FIG. 4(b) is a plan view of the bearing body;

FIG. 4(c) is a side elevational view of the bearing body;

FIG. 5(a) is a vertical sectional view of a roller retainer, taken through an intermediate portion thereof in the longitudinal direction;

FIG. 5(b) is a front elevational view of an end portion of the roller retainer;

FIG. 5(c) is a plan view of the roller retainer;

FIG. 5(d) is a side elevational view of the roller retainer;

FIG. 5(e) is a bottom view of the roller retainer;

FIGS. 6(a), 6(b) show how each loaded roller contacts the track shaft; and

FIG. 7 is a front elevational view of another embodiment of the linear slide roller bearing unit in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The linear slide roller bearing unit of the invention will be described hereinunder through embodiments thereof with reference to the accompanying drawings.

Referring first to FIGS. 1 to 6, which in combination show a first embodiment of the linear slide roller bearing unit in accordance with the invention, a track shaft 1 is attached to a fixed bed, for example, and extends in the longitudinal direction of the fixed bed. The track shaft 1 is provided with loaded roller rolling surfaces 4 to 7 which are symmetrically formed on both side surfaces of left and right ridges 2, 3 respectively projecting from both side surfaces of the track shaft 1 in the directions of the corresponding imaginary oblique lines each intersecting the horizontal axis X--X at an angle of about 45°. Each of the loaded roller rolling surfaces 4 to 7 is constituted by a spherical surface equal in shape to the outer peripheral surface of each roller B having a barrel shape.

A long movable table 8 is constituted by a block member of substantially U-shaped cross-section and is disposed so as to straddle the track shaft 1. The movable table 8 has longitudinal recesses 11, 12 formed in the opposing inner surfaces of skirt portions 9, 10 thereof. Through holes 13, 13 are bored through the ceiling portion of the movable table 8. A tapped hole 14 is bored through one skirt portion 10.

A pair of left and right bearing bodies 15, 16 are respectively interposed between the track shaft 1 and the corresponding skirt portions 9, 10 of the movable table 8. Each of the bearing bodies 15, 16 is constituted by a block member which extends in the longitudinal direction of the movable table 8 and has a substantially square cross-section. The bearing bodies 15, 16 have their outer side surface portions 15a, 15a, 16a, 16a retained within the corresponding recesses 11, 12 by being secured with fixing members such as bolts 17, 17 fitted into the respective through holes 13, 13 from the upper face of the ceiling portion. It is to be noted that a bolt 17a screwed into the tapped hole 14 is employed to adjust a preload. The bearing bodies 15, 16 are provided with guide ridges 18 to 21 respectively projecting from the centers of their inner side surface portions 15b, 15b, 16b, 16b, that is, the centers of their surface portions which are orthogonal to their adjacent surface portions of the track shaft 1. The guide ridges 18 to 21 have a track-like (oval) planar shape and extend in the longitudinal direction of the corresponding bearing bodies 15, 16. Loaded roller rolling surfaces 22 to 25 are formed on one of the side surfaces of the guide ridges 18 to 21 opposing the track shaft 1. The loaded roller rolling surfaces 22 to 25 longitudinally extend in parallel to the corresponding loaded roller rolling surfaces 4 to 7 on the track shaft 1. On the other hand, the guide ridges 18 to 21 are provided on their other side surfaces with non-loaded roller rolling surfaces 26 to 29 longitudinally extending in parallel to the corresponding loaded roller rolling surfaces 22 to 25. The rolling surfaces 22 to 25 are communicated with their corresponding rolling surfaces 26 to 29 through semicircular roller turning portions 30, 30, 31, 31 formed on both end surfaces of each of the guide ridges 18 to 21, thereby constituting four roller recirculating passages. Each of the loaded roller rolling surfaces 22 to 25, the non-loaded roller rolling surfaces 26 to 29 and the roller turning portions 30, 30, 31, 31 is constituted by a spherical surface corresponding to the outer spherical surface of the rollers B each of which has a barrel shape.

Loaded rollers B₁ are in contact with the corresponding loaded roller rolling surfaces 4 to 7 and 22 to 25 on the track shaft 1 and the bearing bodies 15, 16 as shown in FIG. 1. More specifically, the loaded rollers B₁ are in contact with the corresponding loaded roller rolling surfaces 4 to 7 on the track shaft 1 at a contact angle θ of about 45° with respect to an imaginary oblique line passing through the center of each of the left and right ridges 2, 3 of the track shaft 1 so that the loaded rollers B₁ contacting the loaded roller rolling surfaces 4 and 5 (6 and 7) are orthogonal to each other. Further, as shown in FIG. 6, the curvature of each of the loaded roller rolling surfaces 4 to 7 and 22 to 25 may be made larger than that of the loaded roller B₁ (see FIG. 6(a)). It is also possible to make the curvature of each loaded roller rolling surface equal to that of the loaded roller B₁ (see FIG. 6(b)).

The difference in effect between the barrel-shaped roller and the cylindrical roller employed as a rolling element will be described hereinunder. The barrel-shaped roller B has a larger load bearing capacity and a better aligning function than the cylindrical roller. More specifically, in the case of the barrel-shaped roller B, since a spherical surface is employed to constitute both the outer peripheral surface of the loaded roller B₁ and each of the loaded roller rolling surfaces 4 to 7 and 22 to 25, the loaded roller B₁ is in point or line contact with the loaded roller rolling surfaces 4 to 7 and 22 to 25 and therefore is elastically deformed when a load is applied thereto to allow an increase in its load bearing capacity. In addition, the loaded roller B₁ in point or line contact with the loaded roller rolling surfaces 4 to 7 and 22 to 25 can oscillate laterally with its central point as the fulcrum and therefore provides an alignment range as large as the oscillation width.

Roller retainers 32 to 35 are screwed to the respective guide ridges 18 to 21 of the bearing bodies 15, 16 so as to be parallel to the corresponding inner side surface portions 15b, 15b, 16b, 16b. The barrel-shaped rollers B are accommodated and retained in the spaces defined between the inner side surface portions 15b, 15b, 16b, 16b of the bearing bodies 15, 16 and the corresponding inner surface portions 32b to 35b of the roller retainers 32 to 35 so that both end surfaces of each roller B come in parallel contact with the corresponding surface portions. Thus, a plurality of barrel-shaped rollers B effect recirculation while rotating around their own axes along the loaded roller rolling surfaces 22 to 25 and the non-loaded roller rolling surfaces 26 to 29 of the bearing bodies 15, 16. As will be clearly seen from FIG. 6, the barrel-shaped rollers B, which effect recirculation, have both their end surfaces retained so as to be clamped through slight gaps by the inner side surface portions 15b, 15b, 16b, 16b of the bearing bodies 15, 16 and the inner surface portions 32b to 35b of the roller retainers 32 to 35. Therefore, it is possible to prevent any skew (oscillation of the longitudinal axes) of the rollers, thereby making it possible to ensure smooth running of the movable table 8.

The roller retainers 32 to 35 thus serve to allow the barrel-shaped rollers B to be properly recirculated. For this reason, as shown in FIG. 5, the roller retainers 32 to 35 are respectively constituted by cover members 32a to 35a each having a substantially track-like planar shape and totally opened at one of their linear portions. Moreover, the cover members 32a to 35a respectively have linear slide guide portions 32c to 35c for guiding non-loaded rollers B₂ and curvilinear slide guide portions 32d to 35d continuously with both respective ends of the linear slide guide portions 32c to 35c for the purpose of guiding the barrel-shaped rollers B as they turn. It is to be noted that since the loaded rollers B₁ come in contact with the loaded roller rolling surfaces 4 to 7 on the track shaft 1 while partially projecting from the roller retainers 32 to 35, the sides of the roller retainers 32 to 35 opposite to the linear slide guide portions 32c to 35c for guiding the non-loaded rollers B₂ are opened over the entire lengths thereof.

Referring now to FIG. 7, which shows another embodiment in accordance with the invention, the same constituent parts in this embodiment as those in the first embodiment are denoted by the same reference numerals. In the second embodiment, recesses 11', 12' are formed in the opposing inner surfaces of left and right skirt portions 9', 10' of movable table 8'. Bearing bodies 15', 16' of substantially T-shaped cross-section are respectively held within the recesses 11', 12' by two rows of bolts 17', 17'. It is to be noted that a lateral bolt 17a' screwed through one skirt portion 10' is employed to adjust a preload in such a manner that the bolt 17a' is operated to press the bearing bodies 15', 16' toward a track shaft 1' thereby to adjust the contact pressure of loaded rollers B₁ '. Since the construction and operation of the other parts are the same as those in the first embodiment, the description thereof is omitted.

The linear slide roller bearing unit in accordance with the invention, having the above-described construction and operation, offers the following various advantages:

Since as rolling elements the barrel-shaped rollers are employed, it is possible not only to increase the load bearing capacity of the bearing unit but also to allow the bearing unit to have an excellent automatic aligning function. Further, since the barrel-shaped rollers are clamped with slight gaps provided between both end surfaces thereof and the corresponding retaining surfaces, the skew of the rollers can be prevented, so that it is possible to ensure a smooth running of the movable table. Moreover, since the bearing bodies are formed separately from the movable table and are reduced in size, it becomes easy to effect turning and grinding operations when forming the roller rolling surfaces on the bearing bodies. This facilitation of the formation of the roller rolling surfaces makes it possible to reduce the production cost of the bearing bodies. Furthermore, the bearing unit can be readily produced and assembled advantageously, since it is possible to instantaneously form spaces in which the loaded and non-loaded rollers are accommodated and moved while rolling simply by attaching the roller retainers to the bearing bodies. In addition, it is possible to apply a proper preload (pre-compression) to the loaded rollers simply by adjusting the tightening of each screw used for mounting the bearing bodies, as separate elements, to the movable table. Thus, it is advantageously possible to increase the rigidity of the bearing unit as a whole while ensuring a smooth recirculation of the rollers.

Although the invention has been described by means of specific terms, it is to be noted here that the described embodiments are not exclusive and various changes and modifications may be imparted thereto without departing from the scope of the invention which is limited solely by the appended claims. 

What is claimed is:
 1. A linear slide roller bearing unit comprising:a track shaft extending in the longitudinal direction of said linear slide roller bearing unit and having loaded roller rolling surfaces respectively formed on both side surface portions of each of the right and left ridges thereof projecting in the direction of an imaginary oblique line intersecting the horizontal axis at an angle of about 45°; a movable table constituted by a long block member disposed so as to straddle said track shaft, said movable table having longitudinal recesses respectively formed in the opposing inner surfaces of skirt portions thereof; a pair of right and left bearing bodies each constituted by a long block member which is screwed to the corresponding recess in said movable table, each bearing body having a guide ridge projecting from the center of each inner side surface portion of said block member, each guide ridge having one side surface thereof defined as a loaded roller rolling surface confronting the corresponding loaded roller rolling surface of said track shaft and the other side surface defined as a non-loaded roller rolling surface; barrel-shaped rollers adapted to be recirculated along said loaded roller rolling surfaces and non-loaded roller rolling surfaces of said bearing bodies and to come in contact with said loaded roller rolling surfaces on said track shaft when rolling along the loaded roller rolling surfaces on said bearing bodies; and a roller retainer attached to each of said guide ridges so as to face the corresponding inner side surface portion of the associated bearing body and adapted to guide said rollers so that they can recirculate through the space defined between said roller retainer and inner side surface portion, wherein said rollers in the state of serving as loaded rollers are brought into contact with said loaded roller rolling surfaces on said track shaft at a contact angle of about 45° with respect to an imaginary oblique line passing through the center of each of said right and left ridges of said track shaft so that said loaded rollers contacting said loaded roller rolling surfaces on both side surface portions of each ridge are orthogonal to each other.
 2. A linear slide roller bearing unit according to claim 1, wherein each bearing body has its outer side surface portions retained within the corresponding recess in said movable table by being secured with fixing members fitted into their respective through holes which are bored through a ceiling portion of said movable table in a single row in the longitudinal direction of said movable table, said fixing means being received from the upper face of said ceiling portion.
 3. A linear slide roller bearing unit according to claim 1, wherein each bearing body has its outer side surface portions retained within the corresponding recess in said movable table by being secured with fixing members fitted into their respective through holes which are bored through a ceiling portion of said movable table in two rows in the longitudinal direction of said movable table, said fixing means being received from the upper face of said movable table.
 4. A linear slide roller bearing unit according to claim 1, wherein said loaded roller rolling surfaces are communicated with their corresponding non-loaded roller rolling surfaces through semicircular roller turning portions formed on both end surfaces of each of said guide ridges, thereby constituting roller recirculating passages, respectively, and wherein each of said loaded roller rolling surfaces, non-loaded roller rolling surfaces and roller turning portions is constituted by a spherical surface corresponding to the outer spherical surface of said barrel-shaped rollers. 